Tabbed Sealing Member With Improved Heat Distribution For A Continer

ABSTRACT

A tabbed seal as well as a method of manufacture is provided for sealing containers such as bottles, jars and the like. The tabbed seal is formed with a lower sheet-like structure having a non-foam, heat-distributing layer thereon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior application Ser. No.14/226,932, filed Mar. 27, 2014, which is a continuation of priorapplication Ser. No. 13/296,016, filed Nov. 14, 2011, which is acontinuation-in-part of prior application Ser. No. 11/030,275, filedJan. 6, 2005, all of which are hereby incorporated herein by referencein their entirety.

FIELD

The disclosure relates to a pull-tab sealing member for closing themouth of a container, and more particularly to a pull-tab sealing memberwith improved heat distribution during induction sealing to the mouth ofa container.

BACKGROUND

It is often desirable to seal a bottle, jar or other container with aclosure to maintain freshness of the contents thereof or to indicatewhether the container has been tampered with. However, it is alsodesirable that the closure be easy to remove by the user. For example,U.S. Pat. No. 5,433,992, the contents of which are incorporated hereinby reference, describes a top-tabbed closure for a container which has amembrane for sealing the container and a sheet which is bonded to thetop of the membrane, in a manner which leaves a tab portion of the sheetfree. A user seeking to gain access to the contents of the containersimply grips the tab with their fingers and by pulling on the tab, whichis connected to the sheet, can remove the entire closure and access thecontents of the container in a relatively convenient manner.

Referring generally to FIG. 1, a conventional top-tabbed closure isshown generally at the top of a bottle 10 as container seal 100. A crosssectional view of seal 100, taken along line 2-2 of FIG. 1 which is notdrawn to scale, is shown in FIG. 2.

Seal 100 includes a lower section 101, comprising a lower layer 110,which is formed of an adhesive, such as a hot melt adhesive or othersealants, for securing seal 100 to the top of bottle 10. Lower section101 also includes a foil layer 120 and a polyethylene terephthalate(PET) layer 130 between foil layer 120 and sealant 110. Seal 100 alsoincludes an upper section 102. Upper section 102 includes an ethylenevinyl acetate (EVA) layer 170 having a PET top layer 180 disposedthereon. A bottom surface 150 of EVA layer 170 is surface treated andbonded to foil layer 120. Lower surface 150 also bonds a paper releaselayer 140 to EVA layer 170. Thus, release layer 140 prevents EVA layer170 from being completely bonded to foil layer 120 at lower surface 150.Lower surface 150 only bonds EVA layer 170 to foil 120 up to a boundaryline 160 so as to permit a tab portion 200 to be graspable. However,this bond between upper section 102 and lower section 101 is strongenough, so that pulling tab portion 200 can remove all of seal 100 inone piece.

Conventional container seals exhibit several problems. For example, apaper release or information layer can be sensitive to exposure tomoisture. Use of PET release layers alone do not provide a fullysatisfactory seal. Corrosion of foil layers can also present a problem.Also, conventional closures typically require containers to have smoothsurfaces to insure proper bonding and release.

One particular problem is uneven heating during heat sealing steps. Theuneven heating of the heat-activated adhesive is attributed to theuneven distribution of heat between the tabbed and non-tabbed sides ofthe seal. As a result, one side of the seal is sufficiently adhered tothe mouth of the container while the other side is not. The commonsolution to this problem has been overheating (i.e., oversealing) theseal to ensure that both sides of the seal are adhered to the container.However, this common solution presents additional problems in that theclosures will not separate from the container satisfactorily when thetab is pulled which can result in tearing and unsatisfactorilyincomplete removal of the seal from the mouth of the container.Likewise, the use of excessive heat can lead to oozing of the sealingadhesive which in turn can adhere the tab to the seal. This unwantedside effect is sometimes referred in the art as “tab grab” whichprevents the end user from having easy access to the tab for removal ofthe seal from the container.

The shortcomings of the conventional top-tabbed container sealsdescribed above are heightened when the seal is combined in a two-pieceliner and seal assembly. A two-piece liner and seal assembly typicallyincludes an upper portion of a liner, compressing agent, or pulp boardthat is bonded by a wax or other material to an upper surface of a lowerseal portion. The wax holds the liner portion to the seal portion priorto induction sealing. Upon induction heating, the wax melts and isabsorbed by the liner to separate the upper liner portion from the lowerseal portion and the lower seal portion is heat sealed to a containerrim. Upon a consumer opening a cap or other closure, the liner isretained in the cap while the seal remains bonded to the container rim.

When the conventional top-tabbed seal mentioned above is combined with awax bonded liner forming a two-piece induction seal, the inductionsealing window of operation is considerable smaller than a comparable,but non-tabbed wax bonded liner and seal combination. The problems withuneven heating caused by the partial, paper release layer tend toinsulate the wax layer and impede wax absorption over at least a portionof the assembly above the release layer at lower induction settings.Thus, wax may be adequately absorbed on the non-tabbed side of the sealto permit liner separation, but not fully melted and not absorbed on thetabbed side of the seal. This tends to result, in some cases, of a linerthat has not properly separated from the seal above the paper releaselayer. In other cases, if the seal includes a foam layer, the foam tendsto trap heat below it which may also result in the wax not beingadequately absorbed. A common field solution to these problems is anelevated level of induction heating or a longer induction dwell time,which tends to generate a surplus of heat energy in the assembly.However, elevated heating or longer dwell times has an adverse effect onthe performance of the two-piece assembly. For instance, the additionalheat further accentuates the performance shortcomings of the tearing,adhesive oozing, and tab grab mentioned above. Moreover, in a two-pieceliner and tabbed seal assembly, elevated induction heating and dwelltimes can often melt the upper polymer layers of the lower seal portionresulting in permanent adhesion or back bonding of the lower tabbed sealportion to the upper liner portion.

SUMMARY

Generally speaking, a seal and method of manufacture is provided forsealing containers such as bottles, jars and the like. The seal (i.e.,closure) is formed with a lower sheet-like structure having a non-foam,heat-distributing layer thereon. The lower structure includes a foilsupport layer and has a polymer layer, such as a PET film thereunder. Aheat-activated sealant layer is provided under the bottom surface of thePET layer to bond (i.e., adhere) the seal to the opening of a container.Depending on the container being sealed, the PET film may be coated witha suitable material that will bond to various container types. Thenon-foam, heat-distributing layer is a preferably polyolefin film layer.Seals herein also include a top portion, which is partially bonded(directly or indirectly) to the bottom portion, so as to leave a tabportion extending from the seal. The top portion is advantageouslybonded from periphery to periphery of the bottom portion and at orslightly offset from the diameter (middle) of the bottom portion. Thetop portion is advantageously formed with polymer material, such as anethylene vinyl acetate (EVA) layer, having a layer of PET bonded on thetop thereof. A release strip, which can have a release layer coated onthe bottom thereof can be adhered to the top structures and used toprevent the tab from adhering to the lower structure. The release layercan be formed of PET or silicone release coated PET, paper, nylon orpolypropylene.

To form seals described herein, a first laminated sheet of bottomsection material is laminated to a sheet of top section material afterinterposing releasing strips between the sheets. The releasing stripscan be bonded to the top section material and can be printed withwritten material or instructions. The bottom of the releasing strips canbe coated with a release promoting substance, so as to prevent the topsheet from bonding to the bottom sheet at the location of the tabbingstrips. Seals, such as those in the shape of a disc, can then be die cutfrom the sheets. Each disc has approximately half of its area in planview comprising a release strip. The result is a seal with adhesive on abottom side surface and a gripping tab on the top, bonded to half theseal. Such seals can be bonded to the top of containers to seal thecontents thereof. Advantageously, the pull-tab sealing members describedherein exhibit an improved distribution of heat to the heat-activatedadhesive resulting in improved adherence of the sealing member to thecontainer.

Another form of the seal and method of manufacture is provided forsealing containers such as bottles, jars and the like with a two-pieceliner and tabbed sealing member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a conventional closure disposed over themouth of a bottle;

FIG. 2 is a cross-sectional view of the closure of FIG. 1 taken alongline 2-2;

FIG. 3 is a side cross sectional view of a seal;

FIG. 4 is a top plan view of a sheet used to form seals;

FIG. 5 is a cross-sectional view of the sheet of FIG. 4 taken along line5-5;

FIG. 6 is a demonstrative perspective view of an apparatus constructingsheets for forming container seals;

FIG. 7 is a cross-sectional view of an exemplary two-piece liner andpull-tab seal assembly;

FIG. 8 is an exploded, partial cut-away view showing a closure cap witha liner retained therein and removed from a tabbed seal portion adheredto a mouth of a container;

FIG. 9 is a cross-sectional view of a comparative two-piece liner andseal assembly evaluated in Example 4; and

FIG. 10 is a cross-sectional view of another exemplary two-piece linerand pull-tab seal assembly evaluated in Example 4.

DETAILED DESCRIPTION

A pull-tab sealing member (i.e., closure) for a container is showngenerally in FIG. 3 as seal 300. The relative thicknesses of the layersshown in FIG. 3 are not to scale, for purposes of illustration.Furthermore, the construction shown is provided for purposes ofillustration only, and is not intended to be construed in a limitingsense.

Seal 300 is constructed from a bottom laminate sheet 301 and a toplaminate sheet 302. Bottom sheet 301 includes a metal foil, supportlayer 310 having a lower polymer layer 320 on the underside thereof anda non-foam, heat-distributing layer 330 on the top surface thereof.Metal foil support layer 310 is preferably aluminum foil although othermetals can easily be substituted. Support layer 310 is advantageouslyabout 0.0005 to 0.0020 inches thick.

Lower polymer layer 320 is advantageously formed of polyethyleneterephthalate (PET), preferably to a thickness ranging from about 0.0004to 0.0015 inches. Other suitable materials include nylon, PEN andpolypropylene. The bottom surface of lower sheet 301 is advantageouslycoated with a heat-activated sealant or adhesive 340. The type ofadhesive is based in part on the characteristics of the container.Suitable heat-activated adhesives (as used herein, the term sealant willinclude heat-activated adhesives suitable for adhering a container sealto a container) include, but are not limited to, ethylene vinyl acetate,ethylene-acrylic acid copolymers, surlyn and other materials known inthe industry.

The top surface of bottom sheet 301 (layer 330) is advantageouslyprovided with a non-foam, heat-distributing layer 330. Layer 330 isformed of any non-foam, polymeric material that exhibits insulativeproperties as well as resistance to tearing or rupturing upon removal ofthe closure from the sealed container. In a preferred embodiment, thenon-foam, heat-distributing layer 330 is a polyolefin film layer. Thepolyolefin film layer can be a monolayer or a bilayer of two olefinresins co-extruded with a tie layer. Examples of polyolefin resins to beused, include but are not limited to, polyethylene, polypropylene,ethylene-propylene copolymers, blends thereof as wells as copolymers orblends with higher α-olefins. The thickness of the polyolefin film layeris preferably at least about 0.0025 inches (2.5 mil), with at least0.0030 inches (3 mil) being more preferred and at least 0.0035 inches(3.5 mil) being even more preferred. However, the actual thicknessneeded to effect even heat distribution and tear resistance is dependenton the type of polyolefin resin used. As will be apparent to one skilledin the art, polymeric properties such as density and melt index arevariable and will affect the insulative and tear resistance propertiesof the material. In one preferred embodiment, the polyolefin resin to beused as the film layer has a density of at least about 0.96grams/centimeter³ (g/cm³), with 0.97 g/cm³ being more preferred, and0.98 g/cm³ being even more preferred. Overall, the thickness of thepolyolefin film layer should also preferably be no thicker than about0.010 inches, with no more than 0.008 inches being more preferred.Thicknesses greater than these parameters generally increase thebulkiness of the sealing member, provide minimal additional benefit, andare not cost-effective.

Top laminate sheet 302 is advantageously formed with a polymer support350, advantageously including a polymer layer 360 on a bottom surfacethereof. Support 350 is preferably formed from a strong heat resistantsheet-like material, which can maintain its strength at smallthicknesses and which has high pull strength. A preferred material isPET and other suitable materials include PEN and nylon. Polymer layer360 is advantageously formed of EVA and is advantageously from 0.001 to0.003 inches thick. EVA is preferred because of its thermal bondingcharacteristics, such that it readily bonds to layer 330. If layer 360is too thick, it becomes difficult to achieve satisfactory bonds. If itis too thin, bond strength can be inadequate. Other suitable materialsinclude low density polyethylene, ethylene-acrylic acid copolymers andethylene methacrylate copolymers.

Top sheet 302 also includes a tab portion 303. Tab portion 303 is notadhered to bottom sheet 301 and can be folded up and away from bottomsheet 301 to provide a gripping tab for removing seal 300 from the topof the container. Top sheet 302 also includes a joining portion 304which is adhered to bottom sheet 301. A boundary 305 exists at theinterface between tab portion 303 and joining portion 304. Boundary 305advantageously extends in a straight line from edge to edge of seal 300.Boundary 305 is advantageously at or near the middle of seal 300.

The underside of tab 303 advantageously includes a release strip(tabbing strip) 370, preferably having a coat of release material 371 onthe underside thereof. Release strip 370 and release coat 371 helpprevent tab portions 303 from adhering to the top of bottom sheet 301.Release strip 370 is preferably formed of PET, such as white PET andadvantageously includes written material, pictures other informationthereon. Other suitable materials include nylon and polypropylene.Release layer 370 is advantageously 0.00045 to 0.0010 inches thick andpreferably occupies the entire underside of tab portion 303,substantially up to boundary 305. Suitable materials for release coat371 include various known heat resistant coatings preferably siliconerelease coatings.

Bottom sheet 301 is formed by adhering polymer layer 320 to supportlayer 310 with an adhesive. Polymeric heat-distributing layer 330 canalso be adhered to support layer 310 with adhesive. Suitable adhesivesinclude ethylene acrylic acid copolymers, curable two part urethaneadhesives and epoxy adhesives. A preferred adhesive is Morton Adcote 522or Novacote 250. As used herein, the term adhesive will include curableadhesives, heat activated adhesives and thermoplastic adhesives. Topsupport layer 350 can also be adhered to polymer layer 360 withadhesive.

An apparatus for forming a laminated sheet from which seals can beobtained is shown generally as apparatus 600 in FIG. 6.

A bottom sheet 301′ including a support layer 310′ with a top layer ofpolymeric heat-distributing layer 330′ and a bottom polymer coat 320′,having sealant 340′ on the bottom thereof is fed to the nip where apressure roll 610 meets a hot roll 620. A top sheet 302′ is also fedinto the nip between pressure roll 610 and hot roll 620. Top sheet 302′includes a support film 350′ and a polymer layer 360′ on support film350. Top sheet 302′ is fed into the nip between rolls 610 and 620 sothat polymer layer 360′ faces non-foam, heat-distributing layer 330′.Release strips (tabbing strips) 370′ are combined with and insertedbetween top sheet 302′ and bottom sheet 301′ in a parallel spacedarrangement. After heat from hot roll 620 joins top sheet 302′, releasestrips 370′ and bottom sheet 301′, a laminate sheet 400 results.

Laminate sheet 400 is shown in plan view in FIG. 4 and in cross sectionin FIG. 5. The relative size of the layers are not shown to scale andtop sheet 302′ bottom sheet 301′ and tabbing strips 370′ are not shownin a fully laminated joined structure. Also, adhesive between the layershas not been shown. However, those of ordinary skill in the art wouldunderstand how to adhere these multiple layers. To form pull-tab sealingmembers, circular (or other appropriately shaped) portions 410 are diecut from sheet 400. As can be see in FIG. 4, a boundary 305′ isestablished at the edge of each release strip 370′. Because the bottomof release strip 370′ does not adhere to the top surface of non-foamheat-distributing layer 330′, a tab portion will extend from non-foamheat-distributing layer 330′ for gripping.

While not wishing to be limited by theory, it is believed that theadvantages offered by the pull-tab sealing members herein are achievedby disposing non-foam, heat-distributing layer 330 on the side of metalfoil layer 310 opposite from sealant or adhesive layer 340 asillustrated in FIG. 3. The placement of non-foam, heat-distributinglayer 330 redirects heat from induction heating of the metal foil evenlytowards layer 340. The redistribution of heat results in adhesive orsealant being equally activated on both the tabbed and non-tabbed sidesof the pull-tab sealing members. To the contrary, prior art pull-tabseals as illustrated in FIG. 2 allow heat from the metal foil to escapeupwards and away from layer 340 in an uneven manner. The uneven releaseof heat in the prior art seals is believed due to the different heattransfer characteristics exhibited by the tabbed and non-tabbed sides ofthe seal. This in turn results in the uneven activation of the adhesiveor sealant that causes the uneven sealing exhibited by prior artpull-tab seals as illustrated by FIG. 2.

The pull-tab sealing members described herein are sealed to the tops ofcontainers using a heat activated adhesive. The adhesive is heatedthrough induction heating of the metal foil support in the bottom sheetof the seal, such as an aluminum foil support sheet. Tabs formed inaccordance with the disclosure herein, in which the tabbing strip isformed of PET and the non-foam, heat-distributing layer is included onthe foil layer at the interface with the top layer, exhibitssubstantially more even heating and improved sealing.

Moreover, pull-tab sealing members herein will bond to the top surfaceof containers, without the need to oversize the seal and have portionsof the seal extend beyond the top edge of the container, providing aneater appearance. The pull-tab sealing members also provide adequatesealing even when the top surface of the container was not substantiallysmooth, such as in the case of containers having mold lines or otherimperfections on the top surface thereof. The pull-tab sealing membersalso exhibit substantially improved water resistance compared tocontainer seals in which paper is exposed or in which a metal foilsurface is either exposed or covered with only paper. Thus, the pull-tabsealing members offer the additional advantage of reduced corrosion fromexposure to water or juices. An additional benefit of the pull-tabsealing members is that the non-foam heat-distributing layer isolatesand thereby inhibits deterioration to the tab portion of the seal whenthe sealant is heat-activated to adhere the sealing member to acontainer.

Turning to FIGS. 7 and 8, exemplary two-piece liner and tabbed sealingmember assemblies are illustrated using the non-foam heat distributingpolyolefin layer described above. In one approach shown in FIG. 7, atwo-piece assembly 400 includes an upper liner 412 releasably bonded toa lower pull-tabbed sealing member or seal portion 410. Upon inductionheating, the upper liner 412 separates from the lower pull-tabbedsealing member 410 so that the liner 412 may be retained in a cap orother closure 490 (such as a screw cap) and the pull-tabbed sealingmember 410 is adhered to a rim 492 surrounding an opening of a container494 (generally shown in FIG. 8). FIG. 8 shows the cap in a partialcut-away view so that the liner 412 retained therein is visible. Theliner 412 may be retained by threading, protruding members, or otherretention devices on an inner surface of the closure 490.

As described further below, assembly 400 includes a non-foam heatdistributing layer, such as the non-foam heat distributing polyolefinlayer described above. In one approach the non-foam heat distributinglayer has a density and a thickness effective so that the upper linerportion 412 can be separated or otherwise released from the lowerpull-tab portion 410 during induction heating and so that the lowerpull-tab portion 410 forms a bond to a container rim that is effectiveto allow the entire pull-tab portion 410 to be removed from a containerwithout tearing, rupturing, or delaminating of the tab portion from theremainder of the laminate upon a user applying a pulling or removalforce to the tab.

More specifically, one approach of a two piece liner includes the tabbedseal portion 410 having a lower seal laminate 401 and an upper tabbedportion 402. The lower seal laminate 401 includes, starting at thebottom most layer, a sealant layer 440 for bonding to the rim of acontainer. By one approach, the sealant layer 440 may be aheat-activated sealant or adhesive. Suitable heat-activated materialsmay be a mono-layer or a co-extruded layer of ethylene vinyl acetate,ethylene-acrylic acid copolymers, surlyn, and the like as well as blendsthereof that is about 0.5 to about 3 microns thick and configured to beheat sealed to a container rim upon application of induction heating. Byone approach, the sealant layer may be a co-extruded polyethylene withabout 9 to about 20 percent EVA. Sealant layer 440 may also be otheradhesives or bonding layers as needed for a particular application.

Next, a polymer film layer 420 is bonded to an upper surface of thesealant layer 440. By one approach, layer 420 is bonded to layer 440 byan adhesive, such as a two-component polyurethane adhesive. By oneapproach, the adhesive may be coated thereon at a basis weight of about3 to about 5 grams/m². Layer 420 may be a 48 to 92 gauge polyester filmlayer, or layer 420 may be nylon, PEN, and/or polypropylene.

Above layer 420, there is a membrane or induction heating layer 410. Byone approach, layer 410 is aluminum, such as about a 5 to about a 25micron thick aluminum foil layer, but other metals, foils, and materialsmay also be used that have a high thermal conductivity. By one approach,layer 410 is bonded to layer 420 by an adhesive, such as a two-componentpolyurethane adhesive. By one approach, the adhesive may be coatedthereon at a basis weight of about 3 to about 5 grams/m².

Above the membrane layer 410, there is a non-foam heat distributinglayer 430, such as a non-foam heat distributing polyolefin film layer asdescribed in the previous embodiments. By one approach, the non-foamheat distributing polyolefin film layer is a blend of polyolefinmaterials, such as a blend of one or more high density polyolefincomponents combined with one or more lower density polyolefincomponents. Suitable polymers include but are not limited to,polyethylene, polypropylene, ethylene-propylene copolymers, blendsthereof as well as copolymers or blends with higher alpha-olefins. Byone approach, the non-foam heat distributing polyolefin film layer is ablend of about 50 to about 70 percent of one or more high densitypolyolefin materials with the remainder being one or more lower densitypolyolefin materials. The blend is selected to achieve effectivedensities to provide both heat sealing to the container as well asseparation of the liner from the seal.

By one approach, effective densities to achieve both separation of theliner and acceptable sealing of the tabbed seal to a container aresimilar to those of the previous embodiments and include densities ofthe non-foam heat distributing polyolefin layer between about 0.96 g/ccto about 0.99 g/cc. Above or below this density range, unacceptableresults are obtained because the layer provides too much insulation ordoes not effectively distribute heat. By another approach, the non-foamheat distributing layer is a blend of about 50 to about 70 percent highdensity polyethylene combined with low to medium density polyethyleneeffective to achieve the density ranges described above.

In addition, effective thicknesses of the non-foam heat distributinglayer are selected to achieve such performance in combination with thedensity. One approach of an effective thickness may be about 2 to about10 mils. Thicknesses outside this range were unacceptable because thelayer does not provide enough insulation or does not effectivelydistribute heat as needed to achieve the dual performancecharacteristics of liner separation and seal member bonding.

Above the non-foam heat distributing layer 430, there is a partiallayer, tabstock, or tab defining layer 470. The tabstock 470 is notbonded to the non-foam heat distributing layer 430 below it in order toform a tab that is defined wholly within the circumference or perimeterof the lower seal member similar to the embodiments discussed above. Byone approach, the tabstock 470 is a polyester, such as PET. Optionally,the tabstock 470 may include a release coating 471 on a lower surfacethereof.

Next, a bonding layer 460 covers and is bonded to both the tabstock 470and the non-foam heat distributing layer 430. The bonding layer 460combined with the tabstock 470 forms a tab that can be pivoted upwardlysimilar to the discussion on the previous one-piece assemblies mentionedabove. By one approach, the bonding layer may be about 2 to about 3 milsof ethylene vinyl acetate (EVA) or other acceptable bonding materials.Another suitable bonding layer may be ethyl methacrylate (EMA).

Above the bonding layer 460 is an upper protective layer 450, such as alayer of 48 to 142 gauge polyester. PET is one acceptable polyester.Optionally, above the protective layer 450, there may also be anadditional support layer 451, such as another layer of polyester. Alayer of 48 to 92 gauge PET may be suitable for the support layer 451.The use of the optional support layer 451 may aid in providing areinforced pull-tab layer that does not fold over during assembly and ismore durable to withstand heating so that the upper layers of thepull-tab do not melt and back bond to the liner. To this end, densitiesof the protective layer and the support layer may greater than thenon-foam heat distributing layer discussed above. By one approach,densities of layers 450 and 451 may be at least about 1 g/cc and, insome cases, about 1 to about 1.4 g/cc. For instance, with the use of theoptional support layer 451, a support is provided above the foil overthe entire circumference or surface area of the liner that aids inpreventing or reducing fold over or distortion of the liner when it isinserted into a cap or other closure. By one approach, layer 450 isbonded to layer 451 by an adhesive, such as a two-component polyurethaneadhesive. By one approach, the adhesive may be coated thereon at a basisweight of about 3 to about 5 grams/m². Layers 450 (and 451 if used)through layer 440 as shown in FIG. 7 form the lower tabbed portion 410in this example. Layer 451 helps increase the tear resistance of theseal, helps minimize fold over, and increases the stiffness. A 142 gaugelayer 450 may also be used to achieve such functionality.

Forming the second piece of the two-piece assembly is a liner portion412 that is releasably bonded to an upper surface of the lowerpull-tabbed portion 410. This liner portion includes a releasablebonding layer 480 that releasably bonds a liner layer 482 to an uppersurface 481 of the lower pull-tab sealing member 410. By one approach,the releasable bonding layer 480 is a wax layer or a dot matrix of waxthat bonds the liner to the pull-tab sealing member, but allows theselayers to separate upon heating. However, the releasable bonding layer480 may be other materials that form a temporary bond between the twoadjacent portions. The liner 482 may be a fiber, pulp, cardboard,synthetic polymer, foam, or other compressing type layer. By oneapproach, the liner may be 10-40 mils thick.

In one approach, upon induction heating, the non-foam heat distributinglayer 430 has a density and a thickness effective to redistributesufficient heat so that the layer 480 releases or melts substantiallyacross the entire upper surface area of the tabbed seal 410 (includingboth the tabbed and non-tabbed sides of the seal) to a molten state andthen is absorbed by the pulp backing liner 742. At the same time, thenon-foam heat distributing layer also has a density and thickness toprovide sufficient thermal energy to form a desired bond to thecontainer rim. In this case, the heat seal bond to a container is suchthat the lower pull-tab sealing member 410 can be removed from thecontainer in one piece, without tearing, rupturing, or delaminating ofthe tab upon a user applying a pulling or removal force to the tabsimilar to the prior embodiments. That is, the non-foam heatdistributing polyolefin layer 430 is effective to provide the dualperformance of both a more uniform heat distribution above and below thelayer 430 so that the seal 410 is properly bonded to the container andthe wax 480 is effectively melted across the entire surface areas of theseal to adequately separate the liner from the seal over a wideinduction sealing window. By one approach, the wide induction sealingwidow encompasses induction heating dwell times of about 1.2 to about2.5 seconds, which is about a 60 percent larger induction sealing windowthat prior two-piece tabbed members.

Advantages and embodiments of the seals and assemblies herein arefurther illustrated by the following examples; however, the particularconditions, processing schemes, materials, and amounts thereof recitedin these examples, as well as other conditions and details, should notbe construed to unduly limit the seals and assemblies described herein.All percentages are by weight unless otherwise indicated.

EXAMPLES Example 1

A 0.7 mil aluminum foil sheet was adhered to a 0.5 mil PET film withadhesive. A 1.5 mil sealant film was then adhesive laminated to the PETsurface of the foil/PET laminate. The three ply laminate was thenadhered to a 3 mil polyolefin film layer with urethane adhesive to forma bottom sheet. The olefin film layer was a commercially available resinblend sold under the trade name Imaflex® HD Double White PE, which is amonolayer polyethylene film blend of high density and medium density PEwith a 70% by weight high density component. The olefin film waspigmented. The overall density of the film was 0.978 g/cm³. The topsheet was adhered to the bottom sheet with a thermal bonding processafter 0.5 mil PET tabbing strips were inserted therebetween. The bottomside of the tabbing strips was coated with a silicone release coating toinsure that they did not adhere to the olefin film top layer of thebottom sheet. Circular seals, approximately 1.5 inches in diameter, weredie cut from the strips, with the edge of the tabbing sheet extendingapproximately down the midpoint of the circle, to yield tabs having abase running down the middle of the seals, from edge to edge. Thesealing members were induction sealed to containers and produced an evenseal.

Example 2

Following the procedure of Example 1, a 0.7 mil aluminum foil sheet wasadhered to a 0.5 mil PET film with adhesive. A 1.5 mil sealant film wasthen adhesive laminated to the PET surface of the foil/PET laminate. Thethree ply laminate was then adhered to a 3 mil polyolefin film layer,NEX M4129, with urethane adhesive to form a bottom sheet. The NEX (NewEngland Extrusion) M4129 grade film was a monolayer film with a 50% byweight high density component blended with low density polyethylene anda fractional melt index polyethylene. The overall film density was 0.994g/cm³. The olefin film was pigmented. The top sheet was adhered to thebottom sheet with a thermal bonding process after 0.5 mil PET tabbingstrips were inserted therebetween. The bottom side of the tabbing stripswas coated with a silicone release coating to insure that they did notadhere to the olefin film top layer of the bottom sheet. Circular seals,approximately 1.5 inches in diameter, were die cut from the strips, withthe edge of the tabbing sheet extending approximately down the midpointof the circle, to yield tabs having a base running down the middle ofthe seals, from edge to edge. The sealing members were induction sealedto containers and produced an even seal.

Example 3

Following the procedure of Example 1, a 0.7 mil aluminum foil sheet wasadhered to a 0.5 mil PET film with adhesive. A 1.5 mil sealant film wasthen adhesive laminated to the PET surface of the foil/PET laminate. Thethree ply laminate was then adhered to a co-extruded 3 mil polyolefinfilm layer, NEX C4349WH, with urethane adhesive to form a bottom sheet.The NEX C4349WH grade film was a co-extruded bilayer ofpolyethylene/polypropylene resins blended with a plastomer polyolefinfor toughness. The overall film density was 0.989 g/cm³. The olefin filmwas pigmented. The top sheet was adhered to the bottom sheet with athermal bonding process after 0.5 mil PET tabbing strips were insertedtherebetween. The bottom side of the tabbing strips was coated with asilicone release coating to insure that they did not adhere to theolefin film top layer of the bottom sheet. Circular seals, approximately1.5 inches in diameter, were die cut from the strips, with the edge ofthe tabbing sheet extending approximately down the midpoint of thecircle, to yield tabs having a base running down the middle of theseals, from edge to edge. The sealing members were induction sealed tocontainers and produced an even seal.

Example 4

A comparison was performed showing the induction sealing windowachievable using a comparative, conventional top-tabbed two-piece linerto a two-piece liner and seal assembly using the non-foamed heatdistribution layer described herein. The testing used an Enercon CompakJr. induction cap sealer (Menomonee Falls, Wis.). The liner and sealassemblies used in the evaluation are shown in FIG. 9 (comparative) andFIG. 10 (non-foam heat distributing layer). Each assembly was inductionsealed to a 38 mm HDPE bottle (100 cc) with a screw top closure andevaluated over a range of dwell times from about 1.2 seconds to about2.6 seconds.

FIG. 9 shows the comparative liner and seal assembly 600 that does notinclude the non-foam heat distributing layer. This comparative assemblyincludes an upper liner portion 612 bonded to a lower seal portion 610.It will be appreciated that the assembly is not drawn to scale. In thetabbed seal portion 610, there is a lower seal laminate 601 and an uppertabbed portion 602. The lower seal laminate 601 includes, from top tobottom, a 1.5 mill co-extruded polyethylene and EVA sealant layer 620with about 12 percent EVA (New England Extrusion). A 48 gauge polyesterfilm layer 622 is bonded to the sealant layer 620 with about 3.5grams/m² of a two-component polyurethane adhesive (COIM USA). Abovelayer 622, there is a layer of 25 micron thick aluminum foil 624 bondedto layer 622 with the two-component polyurethane adhesive (3.5grams/m²). Above the foil layer 624, there is a partial layer or papertab layer 626. This paper layer 626 is not bonded to the foil 624. Then,a layer of 3 mil thick ethylene vinyl acetate (EVA) 630 covers and isbonded to both the paper layer 626 and the foil layer 624. Above the EVA630 is a layer of 92 gauge PET 632. Layers 620 through layer 632 formthe lower tabbed portion 610. Wax bonded to the tabbed portion 610 isthe upper liner portion 612. This portion includes about 12.5 grams/m²of a wax layer 640 that releasably bonds a pulp backing liner 642 to thetabbed seal 610. Upon induction heating the wax is supposed to meltacross the entire upper surface area of the tabbed seal 610 to a moltenstate and then be absorbed by the pulp backing liner 642. However, dueto the paper layer 626, heat does not properly flow through the laminateto evenly melt the wax across the entire surface area of the assembly.

FIG. 10 shows a liner and seal assembly 700 using the non-foamheat-distributing polyolefin film layer as described and used for theevaluation in this Example. This assembly includes an upper linerportion 712 bonded to a lower seal portion 710. It will also beappreciated that the assembly is not drawn to scale. In the tabbed sealportion 710, there is a lower seal laminate 701 and an upper tabbedportion 702. The lower seal laminate 701 includes, from top to bottom, a1.5 mil co-extruded polyethylene and EVA sealant layer 720 with about 12percent EVA (New England Extrusion). A 48 gauge polyester film layer 722bonded to the sealant layer 720 with about 3.5 grams/m² of atwo-component polyurethane adhesive (COIM USA). Above layer 722, thereis a layer of 25 micron thick aluminum foil 724 bonded to layer 722 withthe two-component polyurethane adhesive (3.5 grams/m²). Above the foillayer 624, there is a non-foam heat-distributing layer of a 2.5 milpolyolefin film 728. Film 728 was a monolayer polyethylene film withabout 70 percent high density polyethylene and an overall density of0.978 g/cm³. (Imaflex Double White PE.) Above the non-foamheat-distributing layer 728, there was a partial layer or PET tabstockor tab defining layer 726. The tabstock 726 was not bonded to thenon-foam heat-distributing layer 728. Then, a layer of 2 mil thickethylene vinyl acetate (EVA) 730 covers and is bonded to both thetabstock 726 and the non-foam heat-distributing layer 728. Above the EVA730 is a layer of 92 gauge PET 732. About the PET layer 732 there is anadditional layer of polyester in the form of a 48 gauge polyester film734 bonded to layer 732 with about 3.5 grams/m² of the two-componentpolyurethane adhesive. Layers 720 through layer 734 form the lowertabbed portion 710. Wax bonded to the tabbed portion 710 is the upperliner portion 712. This portion includes about 12.5 grams/m² of a waxlayer 740 that releasably bonds a pulp backing liner 742 to the tabbedseal 710.

Upon induction heating the wax melts across the entire upper surfacearea of the tabbed seal 710 to a molten state and then is absorbed bythe pulp backing liner 742. In this case, due to the non-foamheat-distributing layer 728, a more uniform heat transfer wasexperienced both above the below the layer 728 and the seal 700 properlybonded to the container and the wax was effectively melted across theentire surface areas of the seal to separate the liner from the sealover a much wider induction heating window that the comparative liner asshown in Table 1 below.

The results of the evaluation are provided in Table 1 below. The Tableidentified seal performance as either acceptable (A) or a failure.Failures were observed and identified in the Table as tab pull off wherethe tab separated from the lower liner portion because the heat seal wasbonded to strongly to the container rim (T), squeeze out of polymer (S),back bonding of the seal to liner due to melting of upper seal layer(BB), or base facing layer tearing upon tab pulling due to excessivebonding of the heat seal layer to the container (BT).

As seen in Table 1, the comparative liner and seal assembly without thenon-foam heat distributing layer had a very narrow sealing window andprovided acceptable performance with a heat seal dwell time window ofonly about 1.2 seconds to about 1.5 seconds. On the other hand, theliner and seal assembly constructed according to the disclosure hereinwith the non-foam heat-distributing layer dramatically increased theoperating window of the induction sealing dwell times to about 1.2second all the way up to 2.5 seconds.

TABLE 1 Induction Sealing Performance Results Dwell Time, Seconds 1.21.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 Assembly ObservedSeal Performance Comparative A A A A BT BT BT BT BT BT BT BT, BT BT, BT,2-Piece liner S, T BB BB and seal without non- foam heat- distributinglayer 2-piece liner A A A A A A A A A A A A A A T and seal using nonfoam heat- distributing layer

It will be understood that various changes in the details, materials,and arrangements of the process, liner, seal, and combinations thereof,which have been herein described and illustrated in order to explain thenature of the products and methods may be made by those skilled in theart within the principle and scope of the embodied product as expressedin the appended claims.

What is claimed is:
 1. A laminate sheet configured to form a tabbed sealing member with improved heat distribution for sealing to a rim surrounding a container opening, the laminate sheet comprising: a bottom laminate sheet including a lower sealant or adhesive coating for securing a formed tabbed sealing member to a container rim, a metal foil layer above the lower sealant or adhesive coating for heating the lower sealant or adhesive coating in a formed tabbed sealing member, and a non-foam, heat-distributing polyolefin film layer above the metal foil layer; the non-foam, heat-distributing polyolefin film layer including at least a high density polyolefin component and having a density from about 0.96 to about 0.99 g/cc; an upper laminate sheet including a first portion secured to the non-foam, heat distributing polyolefin film layer and a second portion not secured to the non-foam, heat distributing polyolefin film layer so that a when a tabbed sealing member is formed out of the laminate sheet a pull tab is defined by part of the upper laminate sheet second portion; a release strip between the upper laminate sheet and the bottom laminate sheet, the release strip secured to the upper laminate sheet but not secured to the bottom laminate sheet to form the upper laminate sheet second portion; and the non-foam, heat distributing polyolefin film layer is a sufficient thickness so that when the lower sealant or adhesive coating of a formed tabbed sealing member is secured to a container, a formed tabbed sealing member can be removed from the container by the pull tab without separating the upper laminate sheet from the bottom laminate sheet or rupturing the non-foam, heat-distributing polyolefin film layer.
 2. The laminate sheet of claim 1, wherein the non-foam, heat-distributing polyolefin film layer is selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymers, and blends thereof.
 3. The laminate sheet of claim 1, wherein the non-foam, heat distributing polyolefin film layer is at least about 2 mils thick.
 4. The laminate sheet of claim 1, wherein the release strip is PET.
 5. The laminate sheet of claim 1, wherein the upper laminate sheet includes a polymer support layer and a layer of EVA under the polymer support layer.
 6. The laminate sheet of claim 5, wherein the layer of EVA secures the upper laminate sheet to the bottom laminate sheet at the upper laminate sheet first portion.
 7. The laminate sheet of claim 6, wherein the polymer support layer is selected from PET, nylon, PEN, and blends thereof.
 8. The laminate sheet of claim 1, wherein the non-foam, heat-distributing polyolefin film layer has a density of at least about 0.97 g/cc.
 9. The laminate sheet of claim 1, wherein the non-foam, heat distributing polyolefin film layer is from about 2.5 to about 10 mils thick.
 10. The laminate sheet of claim 1, wherein the non-foam, heat distributing polyolefin film layer is a bilayer of polyolefins.
 11. A tabbed sealing member including a non-foam, heat-distributing polyolefin film layer for sealing to a rim surrounding a container opening, the tabbed sealing member comprising: a bottom laminate sheet including a lower sealant or adhesive coating for securing the tabbed sealing member to a container rim, a metal foil layer above the lower sealant or adhesive coating, and a non-foam, heat-distributing polyolefin film layer above the metal foil layer; the non-foam, heat-distributing polyolefin film layer including at least a high density polyolefin component and having a density from about 0.96 to about 0.99 g/cc; an upper laminate sheet including a first portion secured to the non-foam, heat distributing polyolefin film layer and a second portion not secured to the non-foam, heat distributing polyolefin film layer to form a pull tab; and the non-foam, heat distributing polyolefin film layer is a sufficient thickness so that when the lower sealant or adhesive coating is secured to a container, the tabbed sealing member can be removed from the container by the pull tab without separating the upper laminate sheet from the bottom laminate sheet or rupturing the non-foam heat-distributing polyolefin film layer.
 12. The tabbed sealing member of claim 11, wherein the non-foam, heat-distributing polyolefin film layer is selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymers, and blends thereof.
 13. The tabbed sealing member of claim 11, wherein the non-foam, heat distributing polyolefin film layer is at least about 2 mils thick.
 14. The tabbed sealing member of claim 11, further comprising a release strip between the upper laminate sheet and the bottom laminate sheet, the release strip secured to the upper laminate sheet but not secured to the bottom laminate sheet to form the upper laminate sheet second portion.
 15. The tabbed sealing member of claim 11, wherein the upper laminate sheet includes a polymer support layer and a layer of EVA under the polymer support layer.
 16. The tabbed sealing member of claim 15, wherein the layer of EVA secures the upper laminate sheet to the bottom laminate sheet at the upper laminate sheet first portion.
 17. The tabbed sealing member of claim 16, wherein the polymer support layer is selected from PET, nylon, PEN, and blends thereof.
 18. The tabbed sealing member of claim 11, wherein the non-foam, heat-distributing polyolefin film layer has a density of at least about 0.97 g/cc.
 19. The tabbed sealing member of claim 11, wherein the non-foam, heat distributing polyolefin film layer is from about 2.5 to about 10 mils thick.
 20. The tabbed sealing member of claim 11, wherein the non-foam, heat distributing polyolefin film layer is a bilayer of polyolefins. 